Ventricular Arrhythmias, by Christine LaGrasta.
Welcome to today's module on arrhythmias.
My name is Christine LaGrasta.
I work at Children's Hospital of Boston as a pediatric nurse practitioner.
Rhythms originating in the ventricle are premature ventricular contraction, ventricular tachycardia,
and ventricular fibrillation.
Characteristics of ventricular rhythms are the QRS complexes are wide and long in duration,
the QRS complexes and T waves often point in the opposite direction of the normal rhythm
QRS complexes, and the QRS complexes are randomly related to P waves.
A premature ventricular contraction occurs when the QRS complex is different-looking
from the sinus QRS complex.
It is abnormal and wide.
It occurs before the next expected QRS complex in a regular rhythm.
The electrical impulse starts in the ventricle and not in the SA node.
There is no P wave before the premature QRS complex.
Causes include electrolyte disturbances such as low potassium and magnesium levels, myocarditis,
cardiomyopathy, and digitalis toxicity.
Treatment.
The occasional premature ventricular contraction or PVC does not require treatment.
Treat low electrolyte levels such as potassium or magnesium when indicated.
There are several types of premature ventricular contractions.
They include bigeminy, couplets, and multifocal PVCs.
Bigeminy occurs when every other QRS complex is a premature ventricular contraction.
A couplet is two premature ventricular contractions occurring together.
Multifocal premature ventricular contractions occur when the premature ventricular contractions
originate from different locations within the ventricle or from both ventricles.
Ventricular tachycardia is three or more premature ventricular contractions occurring together.
The rate is 120 to 180 beats per minute.
The patient may not have a pulse.
This rhythm is considered a medical emergency.
Causes include it can occur with post operative cardiac procedures that involve a ventriculotomy,
for example, tetrology of Fallot, transposition of the great arteries, and Fontan repairs.
This rhythm can also occur with conduction defects, cardiomyopathy, myocarditis, coronary
artery abnormalities, hypokalemia or hyperkalemia, and hypoxia.
Treatment.
If the patient has a pulse, perform synchronized cardioversion.
If the patient does not have a pulse, start cardiopulmonary resuscitation, or CPR, and
defibrillate without delay.
Medications to treat ventricular tachycardia are amiodarone and lidocaine.
Follow the steps of pediatric advanced life support or the PALS guidelines.
Point of clarification.
The correct dose for amiodarone is 5 milligrams per kilogram IV over 20 to 60 minutes with
a maximum of 300 milligrams.
Repeat daily maximum is 15 milligrams per kilogram.
Lidocaine should be administered at 1 milligram per kilogram IV, with a maximum of 100 milligram
per administration.
Ventricular fibrillation occurs when there is an electrical activity in the heart without
identifiable QRS complexes.
There is uncoordinated ventricular contraction without cardiac output.
Therefore, the patient's heart is not contracting, and the patient does not have a pulse.
This, again, is a medical emergency.
Causes include severe hypoxia, hyperkalemia, and myocarditis.
Management is cardiopulmonary resuscitation, defibrillation, and epinephrine.
Point of clarification.
CPR should at least be 100 compressions per minute.
In PALS, the first defibrillation shock is given at 2 joules per kilogram, and the second
defibrillation shock is given at 4 joules per kilogram.
Subsequent shocks may be given at 4 joules per kilogram, or some providers may increase
the dose of subsequent shocks to a maximum of 10 joules per kilogram, or the maximum
adult dose recommended by a particular defibrillator.
The proper dosage of epinephrine is 0.01 milligram per kilogram of the standard 1 to 10,000 concentration.
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